Item- Lum Berry
Ability- Inner Focus
Outrage- STAB, Lum Berry stops Dragonite from being confused , Covers Dragon Types. Base Attack Stat. Not being confused can change the course of battle drastically.
Aerial Ace- Ignore Hurricane, Low Accuracy for Hurricane, Aerial Ace is powered from STAB and Dragonite's 134 base attack stat(Rain can help you, but what if you get hit by a OHKO move? Get into your opponent's head.) . Plus Aerial Ace never misses so that covers if your accuracy gets lower.
Fire Punch- Destroys Ice types, Base Attack stat once again
Ice Beam- Covers those Rock Types, Respectable Special Attack
Hope this helps!